Antioxidant composition and use



ANTIOXIDANT COMPOSITION AND USE David 0. De Pree, Royal Oak, Mich assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application January 26, 1953, Serial No. 333,333

4 Claims. (Cl. 44--74) The present invention relates to antioxidant mixtures, particularly for liquid hydrocarbon-type fuels that are subject to deterioration by contact with oxygen.

Gasoline and diesel fuels are subject to deterioration sometimes fairly rapidly, when exposed to air. The deterioration is evidenced by the formation of gum which deposits on surfaces with which these fuels are in contact. These gums interfere with the filtering of the fuels as by clogging the filters and even cause fuel control valves to stick and spark plugs to become fouled.

Many materials have been suggested for use as antioxidants to prevent or delay the above deterioration. 4-aminodiphenylamine is particularly effective for this purpose and would be a very desirable additive were it not for the difiiculty with which it dissolves in hydrocarbon fuels. Although this antioxidant is quite inexpensive, it is so highly insoluble in hydrocarbons as to baflie all attempts to use it commercially.

Even the use of dissolving aids has not relieved the sitnation. The solubility of the 4-aminodiphenylamine in hydrocarbons is so low that when this compound is dissolved in a mutual solvent in any practical concentration, the resulting solution is not miscible with the hydrocarbon, even when accompanied by wetting and/or dispersing agents.

Among the objects of the present invention is the provision of novel antioxidant formulations that make 4-aminodiphenylamine suitable for commercial use.

Additional objects of the invention include the provision of mixtures of olefin-type liquid hydrocarbon fuels with an antioxidant mixture of the above type.

The above as well as still further objects of the present invention will be more clearly understood from the following description of several of its exemplifications.

It has been discovered that mixtures of '4-aminodiphenylamine with Z-aminodiphenylamine with or without small amounts of 2,4-diaminodiphenylamine make very effective antioxidants for the above type of oxygensensitive fuels, and at the same time dissolve quite rapidly in these fuels. The use of 4-aminodiphenylamine by itself as such an antioxidant appears to be quite hopeless.

On the other hand Z-aminodiphenylamine has an antioxidant eifect which is only a fraction of that of its 4-amino isomer. 2,4-diaminodiphenylamine, although somewhat more effective than the 2-amino isomer, is still far poorer than the 4-amino isomer, particularly in the higher concentrations.

It is quite unexpected, therefore, to find that the mixtures of the present invention show an antioxidant effectiveness not much different from that of the pure 4-amino isomer.

The advantages of the present invention are obtained with mixtures from 30 to 70% of 4-aminodiphenylamine, 30 to 70% of Z-aminodiphenylamine and to 20% of 2,4-diaminodiphenylamine, all percentages being by weight. Best results are contributed when the 4amino isomer is present in amounts from 50 to 60%, the

. 2,742,350 Patented Apr. 1' 7, 1:956.

ice

. with or without the use of ethanol or methanol as a dissolving aid. About 1% ethanol. or methanol by weight of the gasoline is all that is needed to prepare a concen-trate'd (up to 40% solution of the mixture which will mix with gasoline as well as diesel oil. Furthermore, the resulting gasoline antioxidant mixture has an antioxidant eliect which is within 2% of that of the pure 4-amino isomer.

Another very effective example according to the present invention is a mixture of 55% of 4-aminodiphenylamine, and the remainder essentially Z-aminodiphenylamine. This mixture is somewhat less effective as an antioxidant than the three component mixture'described above, but the solubility characteristics are much improved. Thus I can provide stabilized hydrocarbon compositions containing commercially feasible amounts of the above antioxidants, that is about 6 to 10 pounds per thousand barrels.

A feature of the present invention is that the unexpected utility of the above mixtures makes it possible to use ingredients that are not too highly refined. By way of example, instead of mixing a pure 4-aminodiphenylamine with its pure Z-amino isomer, the 4-isomer and 2-isomer can be prepared together and used in the crude form without any further purification unless a slight crystallization or the like is called for in order to change somewhat the proportions of the materials.

Thus by nitrating diphenylamine with a mixture of nitric acid and sulfuric acid, a crude mixture of 2- and 4nitrodiphenylamine is recovered. In most runs the crude mixture also contains a small amount of 2,4-dinitrodiphenylamine. These, mixtures can then be directly reduced to the corresponding amino diphenylamines which are usable as antioxidants without further purification.

The antioxidant-mixtures of the present invention can be dissolved in gasoline or fuel oil in amounts ranging from a maximum of 0.01% by weight to the lowest strength in which it provides a detectable improvement. About 0.0025% to 0.0075% gives very good results. More than 0.01% is entirely unnecessary.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof except as defined in the appended claims.

What is claimed is:

1. A petroleum hydrocarbon fuel for use in internal combustion engines stable to oxidation, consisting essentially of a liquid hydrocarbon fuel normally tending to deteriorate by contact with oxygen and, in quantity sufficient to inhibit such deterioration, an antioxidant composition that is essentially a mixture of from 30 to 70% by Weight of 4-aminodiphenylamine, 30 to 70% by weight of Z-aminodiphenylamine and 0 to 20% by weight of 2,4-diaminodiphenylamine.

2. The petroleum hydrocarbon fuel of claim 1 further characterized in that said antioxidant composition is essentially a mixture of from 50 to 60% by weight of 4-aminodiphenylamine, 30 to 50% by weight of 2-aminodiphenylamine and 0 to 20% by weight of 2,4-diamino diphenylamine.

3. Gasoline normally tending to deteriorate in the presence of oxygen containing, in quantity suificient to inhibit such deterioration, an antioxidant composition consisting essentially of a mixture of 55% by weight of 3 4-aminodiphenylamine, 35% by weight of Z-aminodiphenylamine and 10% by weight of 2,4-diaminodiphenylamine.

4. A gasoline normally tending to deteriorate in the presence of oxygen and between about 0.0025 and 0.0075 per cent by weight of an antioxidant mixture of 50m 60% by weight of'4-aminodiphenylamine, the balance being essentially Z-aminodiphenylamine.

Bartram Mar. 3, 1936 OTHER REFERENCES 7 'I'he'Inhibitory Action of Various Substances on The Deterioration of Olefinic Fuel Spirits During Storagepresented at the World Petroleum Congress, London, on July 19-25, 1933. See Table I. (Copy in 44-50, Div. 64.) 

1. A PETROLEUM HYDROCARBON FUEL FOR USE IN INTERNAL COMBUSTION ENGINES STABLE TO OXIDATION, CONSISTING ESSENTIALLY OF A LIQUID HYDROCARBON FUEL NORMALLY TENDING TO DETERIORATE BY CONTACT WITH OXYGEN AND, IN QUANTITY SUFFICIENT TO INHIBIT SUCH DETERIORATION, AN ANTIOXIDANT COMPOSITION THAT IS ESSENTIALLY A MIXTURE OF FROM 30 TO 70% BY WEIGHT OF 4-AMINODIPHENYLAMINE, 30 TO 70% BY WEIGHT OF 2-AMINODIPHENYLAMINE AND 0 TO 20% BY WEIGHT OF 2,4-DIAMINODIPHENYLAMINE. 